Dewatering aqueous slurries of fine mineral particles is common practice in mineral processing plant operations. Dewatering normally involves a combination of sedimentation and filtration. A majority of the water is removed by sedimentation or thickening, which produces a pulp containing 55-65% solids. Rapid settling of solid particles in a slurry produces a clarified liquid which can be decanted and recycled to the previous process. The settling rate of very fine particles can be extremely slow by gravitational acceleration alone and agglomeration with flocculant to form relatively large aggregates of fine particles, flocs, is frequently performed (for reference purposes, see B. A. Wills, “Wills' Mineral Processing Technology”, 7th Edition, Elsevier, 2006). Filtration of the thickened pulp then generates a filter cake containing 80-90% solids.
Thickeners are commonly used to increase the solids' concentration of a suspension of concentrate or tailings. The mineral particles settle to the bottom of the thickener, and the liquid overflows the top of the thickener. It is usually desired to achieve an underflow with high solids' content and a clear overflow with minimal mineral content. In order to obtain a high solids' underflow and clear overflow, one flocculant or a mixture of different flocculants are used to flocculate fines to increase their settling velocity. The utilization of flocculants can shorten the residence time of fine particles inside the thickener and improve its unit capacity. In the mineral processing industry, some flotation plants encounter difficulties in the thickening operation because a thick fluffy layer of flocculated fine particles/air bubbles/chemicals is formed on top of liquid of the thickener. The layer floats stably on the top of the liquid. When the moisture of the layer is vaporized, a dry fluffy layer with cracks can be observed. Such a fluffy layer floating on the top of the liquid imposes an adverse effect on the dewatering performance of a thickener. It reduces the dewatering capacity of the equipment because the floating fluffy layer occupies a considerable volume of the thickener. The quality of the overflow liquid deteriorates because some fine particles fall out of the floating layer and enter the overflow, resulting in overall process deterioration if the liquid is recycled. Therefore, it is desirable to improve thickening operations by obtaining rapid settling of solids and good overflow clarity of the liquid. To solve this problem, a new dewatering process is proposed.